The present invention relates to improvements in or relating to duplex filtering, and is more particularly, although not exclusively, concerned with transmit/receive duplex filtering for multi-standard mobile terminals.
Conventional single standard systems operate on a single specific frequency band and include a duplex filter arrangement which comprises two filter elements sharing a common port at an antenna connection. One of the filter elements handles the transmit band and the other filter element handles the receive band, both filter elements being designed such that interaction between the two filter elements can be achieved.
However, in multi-standard systems, the duplex filter arrangement must cover a number of different frequency bands. Multi-standard systems are currently implemented by using a different, separate duplex filter arrangement for each standard. Such systems are expensive and incur a size penalty.
It is therefore an object of the present invention to provide an improved duplex filter arrangement which comprises multiple filter elements on a single substrate.
In accordance with one aspect of the present invention, there is provided a duplex filtering arrangement comprising:
antenna means for receiving and transmitting signals;
first filtering means for filtering the received signals;
second filtering means for filtering the signals to be transmitted;
characterised in that the first and second filtering means each comprises an array of filter elements formed on a single substrate, the filter elements having different frequency bands in accordance with a plurality of mobile communications standards.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.